Context : It is expected that Be stars are surrounded by circumstellar envelopes , and that a significant fraction have companions .
Achernar ( \alpha Eri ) is the nearest Be star , and is thus a favourable target to search for their signatures using high resolution imaging .

Aims : We aim at detecting circumstellar material or companions around Achernar at distances of a few tens of AU .

Methods : We obtained diffraction-limited thermal IR images of Achernar using the BURST mode of the VLT/VISIR instrument .

Results : The images obtained in the PAH1 band show a point-like secondary source located 0.280 ” north-west of Achernar .
Its emission is 1.8 % of the flux of Achernar in this band , but is not detected in the PAH2 , SiC and NeII bands .

Conclusions : The flux from the detected secondary source is compatible with a late A spectral type main sequence companion to Achernar .
The position angle of this source ( almost aligned with the equatorial plane of Achernar ) and its projected linear separation ( 12.3 AU at the distance of Achernar ) favor this interpretation .